This invention relates to switch assemblies, and more specifically to an air gap switch assembly with a lever that serves to both control and indicate the position of the air gap switch.
The control of electrical fixtures such as lights is often accomplished by using a solid state electronic device (i.e. a triac) which is controlled by an electronic control circuit. Such devices are safe and generally very reliable. However, since there is no physical open circuit when the solid state device is turned off, the normal leakage current through such a device (or its control circuit) can unknowingly result in a hazardous condition even when the device is in the OFF condition. Accordingly, Underwriters Laboratories (UL) requires that such solid state devices be connected in series with an air gap switch.
Even where an air gap switch, such as the contact of a relay, is used in lieu of the solid state electronic device, the control circuit for the relay is often connected in parallel with the relay. In such a case, there can be leakage current through the control circuit even when the relay is in the open position. For this reason, it is preferable to utilize an air gap switch in series with the relay contact.
In most prior art assemblies, a separate control lever, such as a toggle, is provided to operate the air gap switch. By way of example, the control lever may protrude from the bottom of the cover plate of the device. As shown in FIG. 1, the control lever for such a switch is always visible, which detracts from the appearance of the assembly. Moreover, such a control lever provides no obvious visual indication of the ON/OFF status of the air gap switch, and the user must operate the solid state device in order to determine the status of the air gap switch.
A more satisfactory structure is disclosed in U.S. Pat. No. 3,746,923 to Spira et al. The Spira et al device is a dimmer circuit having a dimmer control slider whose position controls the operation of a solid state device so as to adjust the power level to a load. The air gap switch is connected to a camming arrangement which opens the air gap switch when the slider reaches the lowermost position of its travel. This is an advantageous arrangement since it obviates the need for a separate air gap switch control lever. It also provides an indicator of the position of the air gap switch since the switch will only be open when the slider is in its lowermost position. However, it is sometimes desirable to operate the air gap switch independently of the dimmer control slider.